Templating technique is an effective and efficient method to fabricate polymer microspheres with controllable size and same morphology. As one of polymorphs of CaCO₃, vaterite is the ideal template particle for fabricating microspheres because of many advantages such as their biocompatibility, monodispersed pore size and mild decomposition conditions. In this review, based on introducing the CaCO₃ templates briefly, a recent progress in utilizing the CaCO₃ templates for fabricating microspheres is also addressed according to the selection of raw materials and the applications. Three main routes to load the CaCO₃ cores have been used, such as physisorption, infiltration and co-precipitation. The raw materials can be divided into natural polymer (such as polysaccharide, protein and DNA) and synthetic polymer (such as polystyrene sulfonate, polyvinyl alcohol). The structures of microspheres fabricated by CaCO₃ templates are porous and hollow, and size controlling with uniform morphology. All the particles can be used in various areas included pharmaceutical, drug delivery, biosensors and chemical analysis. In the future, the researches of CaCO₃ templating technique will be greatly promoted by the development of nanotechnology and the requirement of biomedical field to prepare the new kinds of microspheres with extensive applications.

Contents
1 Introduction
2 The introduction of CaCO₃ templates
3 Natural polymer microspheres
3.1 Chitosan microcapsules and alginate microcapsules
3.2 Protein and polyaminoacid porous microspheres
3.3 DNA microcapsules
4 Synthetic polymer microspheres
4.1 The polymer microspheres containing polystyrene
4.2 Polyethylene glycol porous microspheres
5 Conclusion